---

• CCITT Rec. Q.400 Sup.2 (11/1988) – BOTH-WAY WORKING OF THE ANALOGUELINE SIGNALLING VERSION OF SIGNALLING SYSTEM R2
  • 1 Both-way working
    • 1.1 Normal conditions
      • 1.1.1 Double-seizure
      • 1.1.2 Minimum duration of idle state after release-guard
      • 1.1.3 Blocking
    • 1.2 Abnormal conditions
  • 2 Special conditions regarding the interruption control for both-way working